Hi,
I have been asked by a friend about condensation in thermal pane windows. The windows I speak of were sealed at the factory, have a wood frame and for some reason have condensation inside the thermal pane.
Does anyone have an idea of how to correct the problem without having to replace the windows.
Thanks
Brian
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Replies
Nope
Excellence is its own reward!
Unfortuanately, the short answer is no.
If not too bad, tempered windows can be successfully dissassembled and cleaned. Regular glass is usually too badly etched (yes, really etched, not just fogged or dirty) inside to be able to be cleaned. I've tried for many years to find a definitive (not just BS) answer as to the exact chemical or biological etching process that occurs, to no avail.
If you do try the tempered glass, heat an old linoleum knife with a torch till you can bend a 45 deg angle to it, grind fairly thin, then reheat and quench. Use that tool and a heat gun to first remove the insulated panes from the frames, then separate one side of the glass from the Separator. Reassemble on a cold dry day (or flood with dry N2 or Ar if available) when you reassemble with silicone, adding some dissicant to the interior. I've done this for both temperd and reualr glass - as said, the regualr was to etched to be able to be cleaned, plus my clumsy effort broke about 20% in attempted dissassembly. (2 of 10)
Good luck.
Check the brand and age of the pannels. It is often etched in the glass someplace near an edge. It will be faint so you have to look carefully.
Some are warranteed for 10, 20 years or even "lifetime".
Some of those warrantees are pro-rated, some don't even include labour. Luckily ours included labour, but I still had to pay 50% ($30K) to replace all the windows on our south wall when too many started to get condensation in them at the 10-year mark..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Hey Phill.."but still had to pay 50% [$30K] to replace all the windows on our south wall" you've finally impressed me.
That's only $50.00 US,
Not a big deal.
Gabe
30 thousand dollars for 60 thousand dollars worth of windows?
Not really windows, just replacement glass (and a fresh-start warranty)..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
I think my High School had $60K worth of windows
Gordsco
1. How old are the windows?
2. Who made the windows?
3. How were they painted on the exterior? Did the paint "lap" on to the glass
1/16th" to seal the unit?
4. look for the glass code on the aluminum spacer to determine the mfg. I you see
nothing there, look in the corners of the glass.... there may be and etched logo
or mafg name with date.
WINSTALL
AM INTERESTED IN YOUR QUESTION ON IF THE PAINT OVER LAPPED ON TO THE WINDOW. WOULD THAT BE ON THE INTERIOR OR EXTERIOR ? AND i AM WONDERING WHAT DIFFERENCE THAT IT WOULD MAKE
Edited 11/12/2002 2:38:12 PM ET by ARM_STAR
The paint is the "final" seal of the wood sash to the glass. I was just curious. It could be part of the seal failure problem. You don't tell me how old the windows are or who the mfg is???? There may be some recourse on warranty!!! worth looking into. There are usually letters and numbers stamped or printed on the aluminum spacer between the 2 panes of glass. This many times tells who made the window.
Let me know.
WINSTALL
I JUST FINISHED INSTALLING REPLACEMENT GLASS IN CUSTOMER'S HOUSE. THE WINDOW BRAND IS NORCO WE BOUGHT REPLACEMENT GLASS FROM THEM. THEIR GLASS IS SEALED ON EXTERIOR BY GASKET THAT PRESSES INTO A GROVE.THE DEALER SAYS NOT TOPAINT THE GASKET HIS REASON IT INCREASES FAILURE OF COURSE THE PAINTER PAINTED THEM (THAT IS WHAT THE OWNER WANTED). WE ALSO REPLACED SEVERAL SACHS WITH GLASS ALTHOUGH THEY FIT THERE IS A DEFINITE DIFFERENCE IN THE SIZE OF THE SACH . THE NEW ONES ARE LARGER WHY I DON'T KNOW. THEY LOOK BETTER. MY THOUGH IS ALL THE WINDOWS ARE CASEMENT THE GLASS IS LARGER AND WITH ANY SEASONAL MOVEMENT IN THE WINDOW FRAME YOU WILL GET A MATCH BOXING EFFECT THIS STRESS THE SACH OVER TIME TRANSFERRING TO THE GLASS AND THEN YOU CAUSE THE SEAL TO BREAK BETWEEN PANES OF GLASS. I DON'T SEE THIS AS MUCH ON DOUBLE HUNG WINDOWS WHY? POSSIBLY SAME SIZE WINDOW TWICE THE FRAME STRENGTH?
> I DON'T SEE THIS AS MUCH ON DOUBLE HUNG WINDOWS WHY?
Possibly because they're supported on both sides and have no shear force on the glass, whereas casements are held up by one edge, putting maximum shear on that plane.
All in all, any kind of permanently sealed design is a mistake. The old European idea of both inswing and outswing casement sash is better because it gives you access to clean everything.
BTW, it's preferable not to use all caps in discussions, as it's supposed to be reserved for "shouting".
-- J.S.
Interesting that you guys have seen more seal failures on casements. I haven't really paid that much attention.
However, if your theory of force transfer causing the seal failure is accurate, here's another take. The casements may be failing more often because most modern casements (that I have seen) use compression-type weatherstripping. Which means: quite a bit of force needs to be exerted on the sash to get it to the fully closed position. This force tends to weaken glue joints over time. (that's why I always discourage people from using compression-type weatherstrip, but that's a subject for another post!) Similarly, the constant stress could be working against the glass seals, too.
Ragnar
John --
By the way, I agree with you that the double-insulated idea is not the way to go. Double casements or storm sash work just fine, and there are no seals to fail.
Regards,
Ragnar
I built a greenhouse out of failed sliding door glass, they were for the most part thermo units where the seals had failed (although one had blood splatters on the unbroken side - but I digress). I dis-assembled close to twenty glass units; usually the failure could be attributed to the ageing of the seal material which causes it to lose plasticity over time. Of course, the fact that these units slid open and closed thousands of times likely accelerates the problem as the vibration from slamming them shut helps to break the seal between the glass and butyl rubber.
Another likely accelerant is the location of the glass itself. The interior air is in effect a vacuum, wide swings in temperature would both create positive and negative pressure inside the unit which surely would help to shorten seal life.This is also the cycle which causes the condensation in the first place - warm moist air from the interior of the home is drawn into the space and condenses on the cold exterior glass.
Curiously, there were a few units with failed seals (ie.the glass just popped off the rubber without effort) where interior condensation had not occurred. These units must have been located in areas where the temp/pressure swing was minimal.
None of this will likely help though, glass guys don't as a rule re-new units as the cost of labour (this is how we Canadians spell it) heavily out-weighs the cost of a new thermo unit. Also, the cloudy areas are actually etched into the surface as someone noted - window cleaner just won't help. And to think that a couple of hundred years ago glass was a luxury that only the rich could afford.
"When we build, let us think that we build forever." John Ruskin
Broadmeadow:
That's really interesting that some of the units with essentially a failed seal weren't yet condensing. Maybe the dessicant (spelling?) was still doing its job. I've been told that the efficacy of the dessicant diminishes with time.
Some more info on failed seals: I have read (and seen) that larger windows are more susceptible to seal failure than smaller ones due to thermal expansion and contraction issues.
And, as one would expect, the highest number of failures occur on south-facing installations.
The dessicant would likely help but where I live in coastal British Columbia (rainforest) it would likely only buy a little more time until it would be maxed out. As a sidebar, when I was making my own wood windows for my addition I was a little hasty with the brad nailer and shattered the whole window. Of course I was determined to salvage the intact side to lessen my sense of loss. When removing the aluminum channel I noted there was no dessicant inside. In correspondence with the thermo unit supplier they said that the dessicant wasn't really necessary - ie. they manufactured them in controlled conditions - if the seal was broken dessicant would only prolong the inevitable. Just another product with engineered obsolescence.
At least the glass itself won't pollute anything in the landfills.
Dessicant is used to obsorb the moisture in the air that is trapped in the air space when the unit is sealed. It may extend the life of a unit if the seal failure is small and reseals itself quickly but overall it won't have much of an effect.
By the way all dual units will fail in time, most likely 25 to 40 years out, it depends on their exposure to water, heat and cold. The more of these you have the sooner the unit will go. This is why most manufactures warranties run out at 20 years.
I'm coming into this a little late but here's my two cents... Most failed units can be replaced by removing the old galss and replacing it. Try to get the original paper work for the order or at least the order number. Try and order the glass from the window manufactureusing the org. order info that way the thickness (OD) and size will be the same. Plus you should order replacement glazing bead. The old stuff will break!
As to why casements have more seal failure than double hungs, there maybe some truth to the theory of shear on the glass but a bigger reason is that DH's are protected from rain by the screen whereas in casements the screens are on the inside. That extra water getting into the glazing pocket and attacking the seal is death to DG units.
Thermal expansion does cause problems by stressing the seal, and more heat -cold cycles will cause faster failures. PPG's Intercept system minimizes this to a degree by having hardset sealants and a flexible spacer.
hi All,
Planning to start construction in No. Calif. on the coast and have many questions about windows.
Are double hang better than Casement with awning?
For exterior should it be vinyl v.s. wood?
The nearest town is a couple hours out so service is questionable...That makes chosing a brand such as Anderson, Marvin or Pella??? We will do installation ourshelves...
Choices...???Help
Double hung vs. casement mostly depends on your house design. Neither one is better than the other. Casement give you more open space, double hungs don't swingout into walkways. You can go on and on with features and benefits but it all comes back to the style of your house and your individual tastes.
I would stay away from wood exterior windows and doors unless you really enjoy painting. Aluminum cladding is quickly replacing painted exterior on wood windows and doors. It is very durable and comes in a large range of colors. Andersen makes a decent product with vinyl clad but watch out because they paint their door panels, double hungs and any custom shapes. They say it is vinyl paint whatever that is!
As far as installing..I assume that you having a General Contractor build the house. He will most likely do the install. I would let him. If you do it he'll be off the hook if the install leaks or they don't work correctly.
The best Thing to do is find several full service window and door stores and check out the options. If you can go and see the installed product. Good luck.
Casements are easier to get weathertight. You can use a lot more compression on the weatherstripping with casements, because they don't have to slide against it. Being on metal hinges, they close to a much more precisely repeatable position.
-- J.S.
Have to disagree with you John on this one. When they do wear out, they are the worst. (and wear out they will)
Gabe
I have both casements and double hung on my 1926 fixer, and of course neither can withstand decades of neglect. But the double hungs seem to fail first, and are more likely to have been converted to fixed lite by somebody with a caulking gun. ;-) Comparing old but operable ones, the double hungs leak more air when the wind blows, and more water when it rains. With good hinges and latches, you can really squeeze the weatherstripping down tight on a casement, but that amount of compression would make it impossible to open or close a double hung unless you made a solid steel sash and moved it with a bottle jack.
-- J.S.
John,
This is just my opinion, but you seem to be a thinking guy, so I'd figure I'd share it with you..... ;)
I prefer using double-hung windows on the weather side of houses because the upper sash gets tucked behind the blind stop. An out-swinging casement can have no stops, so you have to rely soley on the effectiveness and longevity of the weatherstripping.
And regarding weatherstripping, I categorically avoid compression types. Pretty much by definition, compression WS requires that you push or pull the window sash or door to get it to fully close and latch. This pressure works on every one of the glue joints over time, leading to failure at the joints, and then moisture entry and rot.
I highly recommend using leaf-type WS so that contact is made without compression. The "historically accurate" approach calls for spring bronze, but I find using teflon leaves to be easier and more effective. Instead of dozens of tiny nails, they insert into a narrow kerf and hold remarkably well due to a barbed shank.
Regards,
Ragnar
A lot depends on the kind of weather you get and the kind of maintenance the windows will have. Here the rain is more a horizontal than a vertical phenomenon, it's wind-driven to such a degree that any sliding design that's loose enough to operate is also loose enough to leak. Without weatherstripping, water will readily be pushed upward half an inch past a stop and over the top of a sash.
If a glue joint is well made and kept painted, it shouldn't have any problem with the compression. Of course, weatherstripping does need to be replaced from time to time.
Given no maintenance, operating the double hung window will wear through its paint, exposing the wood all along the stiles and stops. If the window is reasonably tight, that wood will get wet, swell up, and the window is stuck shut while it rots. If the window is loose enough, it'll remain operable and leak. Either way, that lets a lot of water into the glue joints. On my windows, the worst glue failures are on the double hungs. The zero maintenance casement has the disadvantage that the sash is supported on one side only, so there's shear acting against its glue joints. Given paint failure, even without compression weather stripping, that is a source of joint failure. But the similarly neglected double hung only suffers that kind of differential loading between the time the first sash cord breaks and the time the second one breaks, and thereafter when it's propped open with a stick on one side. ;-)
On the other hand, given moderate maintenance, the casement window's glue joints are adequately protected, while the double hung is painted shut. ;-)
Really good maintenance is more work on the double hung, because the only right way to paint it is to take it apart, pulling the stops and sash out. Open a double hung a little way (if you can) and look at the sides of the parting rails that face the glass. Approximately 99.44% of them will have very old paint, crud, and drips of newer paint on those surfaces, because they were painted in place. Casements can be adequately prepped and painted in place, because you have complete access to all the surfaces you need to scrape and sand. If you do want to pull the sash, it's easier because it's just hinges. You can pull the hinge pins, or for a really nice job, take all the screws out and clean and polish the hinges separately.
I have both casements and double hung on three sides of my house, all original (the original design was really a hodgepodge). In general, it's the casements that have held up better after 77 years in a moderately to poorly maintained rental building.
-- J.S.
John,
Without weatherstripping, water will readily be pushed upward half an inch past a stop and over the top of a sash
That's some serious rain! Don't you live in California? Have you actually seen this happen with certainty? Are you sure that the water isn't, for example, getting into the wall above the window and soaking through?
I'd also have to figure that any storm that could drive water over the top of a closed double-hung window would also get by weatherstripping.
In normal cases, I still think a double-hung window is less susceptible to water intrusion. Like you said, there's a 1/2" of vertical contact distance between the exposed face of the sash and the top of the sash. On a casement, there's no overlapping protection, just a gap of 3/32" or so at the top of the sash which is completely open to wind-driven rain. The gap at the top is a problem that I've had to deal with on a number of occasions on storm sash or casement sash. So far, I've never seen it happen with double-hungs.
It's interesting that your house seems to have fared much better with the casement sash. Were the sash in either window type constructed the same way (for example, were the casements made with blind tenons instead of fork tenons, etc.)? In my experience, I've seen about equal incidences of rot on casements and double-hungs. It's possible, too, that since they were painted shut for so long, the bottom rails on the DHs rotted more readily since any water driven under them didn't easily weep back out. It's ironic sometimes that a large enough gap - although it lets more water in - also lets it out so readily that rot doesn't occur.
Regarding weatherstripping types, I still think that leaf-types are the way to go. They can be installed on the sides of double-hung sash (or between the exterior face of the sash and the inner face of the blind stop), whereas compression types obviously have no effect here. On traditional casements, leaf-types will keep water from getting deep in the clearance gaps, whereas with compression types the clearance gaps remain fully vulnerable over their entire depth. Also, the leaf-types can be installed on casement windows without exerting any force to speak of on the sash itself. I know you said you think that a well-constructed sash will hold up to the pressures of compression weatherstips. I suppose that one could install the compression types such that excessive force would not be required to close the sash. But in the factory units that I have come across, it does in fact, take a great deal of force to shut them. Why subject the sash to this unnecessary burden?
I agree with you that casements are a lot easier to paint. Most of the original double-hungs sash I encounter isn't even painted on the edges and the 1/2" or so that is more or less covered by the blind stops. Additionally, the check rails are typically unpainted. I think the window sashes were dipped in some sort of (now illegal) sealant in the factory, but that was it - it must have been some pretty good stuff! And many times, the section of jamb hidden by the upper sash is entirely unpainted as well. I'm pretty sure that the original method of painting DHs was to simply close them and paint whatever was exposed. I believe a friend of mine (who is a sash manufacturer) has an old book that outlines this approach, too.
Regards,
Ragnar
> That's some serious rain! Don't you live in California? Have you actually seen this happen with certainty?
Yes, in L.A. We do get a lot of wind with our rain, 25 - 30 MPH with gusts to 40 or even 50 sometimes. Of course with leaks nothing is certain, but those DH's were fairly loose at the time, and had no weatherstripping.
> I'd also have to figure that any storm that could drive water over the top of a closed double-hung window would also get by weatherstripping.
This is where the compression advantage comes in. I haven't measured, but guessing maybe 10 pounds per linear inch.... That's why submarine hatches are outswing on loose hinges, with serious weatherstripping and mechanical dogs all around, and you have to spin that wheel a long way to get them tight.
> On a casement, there's no overlapping protection, just a gap of 3/32" or so at the top of the sash which is completely open to wind-driven rain. The gap at the top is a problem that I've had to deal with on a number of occasions on storm sash or casement sash.
Yes, that gap is the big problem. The way my new windows came is with a compression strip in the stops, and a flap type of strip in the outboard edge of the sash to try to keep water out of the gap. The compression strip stops water, and it also stops enough of the air to reduce significantly the amount of water that gets wind-driven into the gap
> It's interesting that your house seems to have fared much better with the casement sash. Were the sash in either window type constructed the same way (for example, were the casements made with blind tenons instead of fork tenons, etc.)? In my experience, I've seen about equal incidences of rot on casements and double-hungs.
Both are fork tenons. Your experience may be a case of only sick people go to the doctor. Given either design, people only call you when their windows need help. Have you seen cases with DH upstairs and casement downstairs on the same wall? Or a big room with with casements and DH in the same wall? I have two such rooms, and in the downstairs one, the DH's were long ago replaced with those miserable glass louvers. I I'm going all casement in part to have a more unified look.
> It's possible, too, that since they were painted shut for so long, the bottom rails on the DHs rotted more readily
Yes, but the parting rails were also in bad shape. Being narrower than any rails on the casements could be a contributing factor.
> Regarding weatherstripping types, I still think that leaf-types are the way to go. They can be installed on the sides of double-hung sash (or between the exterior face of the sash and the inner face of the blind stop), whereas compression types obviously have no effect here. On traditional casements, leaf-types will keep water from getting deep in the clearance gaps, whereas with compression types the clearance gaps remain fully vulnerable over their entire depth.
I'd agree, put leaf on the double hungs. But on the casements, why not both?
> But in the factory units that I have come across, it does in fact, take a great deal of force to shut them. Why subject the sash to this unnecessary burden?
I don't know that I'd call it unnecessary. If it serves to stop wind driven rain that would push past leafs, perhaps it's a good tradeoff.
> Most of the original double-hungs sash I encounter isn't even painted on the edges and the 1/2" or so that is more or less covered by the blind stops. Additionally, the check rails are typically unpainted.
Our experiences have been different here. Most of the DH's I see are anywhere from quite paint-sick to painted shut. I do remember finding an unpainted surface once, I think it was the top of the top rail of the upper sash. That was on a window in a relatively sheltered location.
> I think the window sashes were dipped in some sort of (now illegal) sealant in the factory, but that was it - it must have been some pretty good stuff!
Wow, I want about 55 gallons of that stuff, whatever it was... ;-)
This has been quite an interesting discussion.....
Thanks --
-- J.S.
The way my new windows came is with a compression strip in the stops, and a flap type of strip in the outboard edge of the sash to try to keep water out of the gap.
It sounds like the "flap" is what I refer to a leaf-type weatherstrip. It sounds like a good window - two layers of protection!
Thanks for all the comments, and keep on applying your brain to projects like you do.
Regards,
Ragnar
Find out who the manufacturer was and order some replacement glass, If you can't find the manufacturer find out who in your area makes insulated glass, remove a unit and take it to them. It is not easy if you do not know who made the unit.